Pull down jaw

ABSTRACT

A pull-down jaw comprising two rectangular plates. Flexible elements engage the plates for lifting of one of the plates relative to the other plate, and bracing devices extending between the plates.

United States Patent 1 1 1111 3,866,898

Spengler Feb. 18, 1975 1 EULL DOWN JAW 2,274,428 2/1942 06111., 269/138 [76] In entor: Ernst Spengle zeughausstrasse 6, 2,987,972 6/1961 Schneider 269/137 Lgnzburg, Switzerland FOREIGN PATENTS OR APPLICATIONS [22] Filed: p 16 1973 99,630 4/1925 Austria 269/136 [211 App]. No.: 351,562 Primary ExaminerRoy Lake Assistant Examiner-Mark s. Bicks 152 U 5 c1 269/138 Ammeyv [51] Int. Cl B23q 3/00 1581 Field 611 Search 269/134, 136, 137, 138 [571 ABSTRACT A pull-down jaw comprising two rectangular plates. [56] References Cit d Flexible elements engage the plates for lifting of one UNITED STATES PATENTS of the plates relative to the other plate, and bracing 593,681 11/1897 Obernesser 269/138 dev'ces extendmg between the plates 1,405,306 1/1922 Martin 269/138 1 Claim, 6 Drawing Figures PATENTED FEB] 81975 sawznrz PULL DOWN JAW BACKGROUND OF THE INVENTION 1. Field of the Invention The invention concerns a pull-down jaw made from two nearly equal rectangularly plates which are parallel with respect to one another, with flexible elements which engage with both plates and serve to lift one of the plates, as well as screw joints which permit bracing of the plates at a slant with respect to the longitudinal side.

2. Description of the Prior Art During clamping of work pieces, especially in screwor clamping vices, the work piece tends to lift with the lateral pressure of the clamping jaws. It was found to be disadvantageous, especially with mass production, that during clamping not all pieces are at the same level, making it necessary to adjust the position of the machining tool.

According to a familiar method, a pull-down jaw which, at the instant of clamping, makes a downward movement in a perpendicular direction with respect to the direction of force, is mounted ahead of the clamping jaws at the backside of the work piece.

SUMMARY OF THE INVENTION The object of the invention is a pull-down jaw which consists of largely dissimilar components, is easy to manufacture and to mount, and, in addition, permits to clamp 21 work piece to the upper section of the jaw alone without the clamping surface falling off. This makes it possible to work on the work pieces in a larger work area.

This is achieved with a pull-down jaw of the type mentioned above, which is characterized by the two plates being provided with at least three, preferably four bracing devices whereby one section of each bracing device is assigned to one of the plates and terminates in a spherical calotte or a truncated cone with straight or concave generatrices, and the other section of the same bracing device, which is assigned to the other plate, consists of a funnel-shaped cavity or an indentation, each with straight or bulging generatrices, the plates bracing each other on these bracing devices only when not under load, but adjoining each other with their plate surfaces as reference surfaces when under load.

A preferred form of execution may be characterized by at least one, preferably both, longitudinal sides of the plates being offset once in form of a step with respect to the other plate, and by a groove which extends over the whole longitudinal side and which is inclined opposite the longitudinal side against its base plane at an angle of up to 8 in the direction of the nucleus of the plate being provided at the inner edge of the step, whereby one steel spring band, each, is clamped into two opposite grooves, respectively.

Another preferred form of execution may be characterized by the two opposite reference surfaces of the plates each being provided with a notch-shaped groove which run extends in trasversal direction with respect to the lifting device and which when joined encloses a parallelogram which contains the flexible element that is braced against one of the plates and acts in the direction of the lift-off.

BRIEF DESCRIPTION OF THE DRAWINGS The drawing illustrates two examples of execution of an object of the invention, wherein:

FIG. 1 is a top view of a pull-down jaw, seen in the direction of the effect of the clamping force;

FIG. 2 is a sectional view taken along the place of line II-II in FIG. 1;

FIG. 3 shows a top view of a second variation of execution of a pull-down jaw, seen in the direction of the clamping force;

FIG. 4 is a sectional view taken along the plane of line IV-IV in FIG. 3;

FIG. 5 is a sectional view taken along the plane of line V-V in FIG. 3, and

FIG. 6 is a sectional view through the grooves and the steel spring bands of the longitudinal sides at a larger scale.

DETAILED DESCRIPTION OF THE INVENTION The pull-down jaw consists of the two plates 1 and 2 which lie parallel to each other. When under load, both plates adjoin each other with their refernece surfaces 21 and 22 which guarantess similar clamping of the work pieces at all time. At the same time, however, the four two-section bracing devices 4,5,6, all four of which are constructed in the same manner, but whose sections must be mounted in equal pairs with respect to the two plates, also adjoin each other.

In the following, the bracing device which is shown in FIG. 1, upper left, and in FIG. 2 upper part, is discussed in more detail. Screw 4 is screwed into thread 3 in plate 2 deep enough for the head to disappear and for the end 5 to project beyond plate 2. This screw end 5 is designed as a spherical calotte. The second section of this bracing device consists of a funnel-shape or conical indentation 6 of the second plate 1 which is approximately opposite screw end 5. Plate], as shown in FIG. 2 is lifted somewhat with respect to plate 2 by means of spring 7, whereby the plates are also kept somewhat apart from one another. The lower part of spherical calotte 5 shown in FIG. 2 is seated on the lower part of indentation 6 at A. When a force K acts on plate 1, indentation 6 slides off calotte 5, and plate 1 is shifted in the direction of arrow V, until calotte 5 sits completely, i.e., over its whole girth on the wall of indentation 6, i.e., reference surfaces 21 and 22 abut each other and take over the full force transfer.

Centering occurs through the force of clamping of a work piece when, for any reason, the two plates become shifted transversally with respect to one another, i.e., each spherical calotte slides into each of the indentations acting as ball socket, so that in this case, too, the two plates 1, 2 abut each other with their whole sur faces. The height of the spherical calotte corresponds to the depth of the ball socket.

As shown in the lower part of FIG. 2, screw 4' with its calotte is screwed into plate 1, while plate 2 is provided with indentation 6.

Instead of screw end 5, the screw head, designed as spherical calotte, may be slotted, too. In this case, the screw must be screwed into the plate from the other side.

The rest of the construction of the pull-down jaw is characterized by the two plates 1 and 2 each being provided with a notch-shaped groove 8,9 which run transversally with respect to arrows K and V, and which during assembly of the plates enclose a parallelogram, as shown in FIG. 2, in cross-section. It contains two spring elements 7 in the shape of a V-shaped steel spring. The ends of the spring press against the walls of groove 9, the flexing section presses on the wall of groove 8. In this manner, plate 1 is lifted against the direction of arrow V while plate 2 is held tight.

The two plates are connected with one another through screws 17 in order to prevent their falling apart. Hereby, some mutual play is to be allowed so that the spherical calottes may emerge somewhat from the indentations.

Bolts 18 serve for centering of the pull-down jaw, so long as screw 19 is attached to a vice jaw.

As shown in FIG. 2, the gap between plates 1 and 2 which is open all around when the pull-down jaw is not under load, is covered up by means of a closed rubber hand 12. This prevents intrusion of dirt and workshavings between the plates. In that section which is covered up with the elastic, highly heatproof band 12, lubricant may form a lubricating film for the friction surfaces of the bracing elements and springs.

The embodiment according to FIGS. 3-6 once again makes reference to rectangular shaped plates 10, 20,

which when under load, are centered with respect to one another through four bracing devices. These bracing devices consist of screws 40 whose ends are designed as truncated cones 50 with straight-lined generatrices. The generatrices may also be concave-shaped. The counterpart to the truncated cone is one indentation 60 for each cone whose generatrices run straight or bulging.

The generatrices of opposite sections of a bracing device must either have the same curvature, or must at least be curved in the same sense.

The two plates are held together, with some play, through four screws 17 each of which are located close to a corner, lest one plate tilts even when small work pieces are clamped.

Screws 19 are provided for attachment to jaw of a vice or clamping vice. The broadsides are sealed by screwed-on covers 14.

At the longitudinal sides, springs 70 made of steel spring band are provided, serving as the flexible element which lifts one plate when the pull-down jaw is not under load. These band springs 70 are clamped into grooves 90 and 19 which run in longitudinal direction.

As shown in FIG. 6, each longitudinal side of each plate 10, 20 is offset once in step-shape against the other plate. A groove 90, 91 which extends over the whole longitudinal side is provided near the inner edge of the step, whereby the grooves are inclined with respect to the longitudinal side against their base plane at a steep angle a of up to 8 in the direction of the nucleus of the plate. The two steps of the same plate are of different width. At the same time, the two plates are mounted in such a manner that, on one longitudinal side, a wider step is always opposite a narrower step. FIG. 6 shows clearly that one plate is offset somewhat, in parallel, with respect to the other plate, due to the slant of grooves 90, 91 the curvature of the band spring 70, and unequal depth of the steps. This offset is, as already discussed, cancelled under load, which results in the desired effect of the pull-down jaws. In order to vary the spring force, spring bands of different thickness are employed.

As shown in the various embodiments, the bracing devices are mounted preferably in the same fashion alongside a side edge of the pull-down jaw, while the other two are offset by The pull-down jaws according to the invention afford a high repeat-accuracy during mass-productionclamping of work pieces, whereby, at the same time, the work pieces do not slip upwards.

A latitude of modification, substitution and change is intended in the foregoing disclosure, and in some instances, some features of the present invention may be employed without a corresponding use of other features.

I claim:

1. Pull down jaw comprising two nearly equal size rectangularly shaped plates abutting each other, flexible elements engaging said plates for lifting of one of said plates relative to the other, screw joints for permitting bracing of said plates at a slant, said plates being provided with a plurality of bracing devices, one section of each bracing device terminating in a generated surface while the other section of the same bracing device is an indentation engageable by said generated surface, said generated surface being a truncated cone including an end of a screw which is mounted in one of said plates nearly perpendicular thereto, said plates bracing one another on these bracing devices only when not under load but abutting each other when under load, said plates including tapered cooperating grooves therein, said grooves being inclined at an angle of up to 8 in the direction of the nucleus of said plates, and said flexible elements being steel spring bands that are bent in the center thereof and clamped into said cooperating grooves. 

1. Pull down jaw comprising two nearly equal size rectangularly shaped plates abutting each other, flexible elements engaging said plates for lifting of one of said plates relative to the other, screw joints for permitting bracing of said plates at a slant, said plates being provided with a plurality of bracing devices, one section of each bracing device terminating in a generated surface while the other section of the same bracing device is an indentation engageable by said generated surface, said generated surface being a truncated cone including an end of a screw which is mounted in one of said plates nearly perpendicular thereto, said plates bracing one another on these bracing devices only when not under load but abutting each other when under load, said plates including tapered cooperating grooves therein, said grooves being inclined at an angle of up to 8* in the direction of the nucleus of said plates, and said flexible elements being steel spriNg bands that are bent in the center thereof and clamped into said cooperating grooves. 